There are numerous optical systems available for examining, in particular for measuring, the geometry of pipes, canals, preferably fresh water pipes with a diameter of approximately 30 mm to about 1500 mm, all of which permit only imprecise imaging and measurement of the actual contour of the interior of the pipe.
For example, state of the art are camera systems on inherently movable platforms with a focal direction oriented in the moving direction, allowing in this manner at least purely visual examination, which gives a rough impression of the composition and geometry of the interior wall of the pipe.
Also state of the art are inspection systems which are provided with a laser light source in addition to the camera system on the inherently movable platform. The laser light source projects a visibly perceivable ring onto the interior wall of the pipe in the field of vision of the camera.
The images taken by the camera unit are stored and evaluated offline, i.e. after measurement, with the aid of special evaluation software. Ultimately, however, image evaluation again resorts to estimated dimensions. Consequently, the information value of the obtained results leaves room for improvement.
Another possible manner of inspecting the interior walls of pipes is put forth in EP 0 725 921 B1, which describes a system for three-dimensional measurement of inaccessible hollow spaces, such as preferably pipes. In this case, a tilted pivoting head is mounted on an inspection vehicle which is insertable in the respective to-be-inspected pipeline. Attached to the pivoting head are usually camera systems to vary the focal direction. Alternatively or in combination, a light section sensor is located on the tilted pivoting head in order to measure the depth of the respective pipeline. This light section sensor permits very precise measurement of the distance from the interior wall of the pipe based on trigonometric principles. Covering the entire pipe wall, however, usually requires time-consuming pivoting of the tilted pivoting head which, in addition, is provided with a very complex, motor-driven articulation.
In DE 94 05 098 A1, in order to examine hollow bodies, the light paths of two triangulation sensors, which for their part are affixed outside the to-be-examined hollow body, are introduced into the interior of the hollow body via a sensor rod and deflection mirrors attached thereto in a desired manner.
US 2004/0114793A1 describes a method for examining pipe-shaped bodies, in which method a laser diode is borne concentrically to a pipe. The laser beam of the laser diode is projected radially to the interior wall of the pipe and imaged via a field lens onto an imaging sensor.
US 2003/01 98 374 A1 describes a device for examining pipelines, which device can be moved through the interior of a pipeline by means of an inherently movable platform. The platform is provided with light sources whose light reflected at the interior wall of the pipeline is detected by light sensors. The optical elements are accommodated in a gas-tight housing in which the optical elements are borne in a vibration-dampened manner via affixing elements.